Optical micro structure, method for fabricating the same and applications thereof

ABSTRACT

An image sensor comprises a plurality of color filtering elements, a plurality of lenses and an image sensing device, wherein the lenses are correspondingly formed over the color filtering elements, and the image sensing device having a sensing area engaged with the color filtering elements.

FIELD OF THE INVENTION

The present invention relates to an optical microstructure and thefabricating method of the same and the applications thereof, and moreparticularly to an optical microstructure applying for manufacturing animage sensor and the method for fabricating the same and theapplications thereof.

BACKGROUND OF THE INVENTION

By virtue of the technical improvement and increased requirement ofconsumer electrics with image processing functions, such as digitalcameras, scanners or smart phones, the demand for image sensors iscontinually growing.

Generally, image sensors can be divided into two types, front sideilluminated image sensors and backside illuminated image sensors.

Since the sensor array of a front side illuminated image sensor isdisposed on the front side of a semiconductor substrate, over which aplurality of inter-metal layers are formed, the incident light enteringthe image sensor must pass through gaps in the inner-metal layers, andthe light is obstructed by the inner-metal layers and cannot bedelivered efficiently to the sensor array, thus the quanta efficiency ofthe front side illuminated image sensor can be inversed effected.

In comparison to a front side illuminated image sensor, the incidentlight of a backside illuminated image sensor is arranged to entering theimage sensor through the backside of the substrate rather than passingthrough the inner-metal layers, such that most of the incident light canbe delivered to the sensor array without any obstruction. Thus thequanta efficiency of the backside illuminated image sensor issignificantly better than that of the front side illuminated imagesensor.

However, fabricating a backside illuminated image sensor requiresadditional procedures in contrast to fabricating a front sideilluminated image sensor. For example, fabricating a backsideilluminated image sensor requires a substrate thinning procedure after ahandle wafer is bound on the front side of the inner-metal layers.Besides, the existence of the handle wafer may obstruct the subsequentpackaging process from making the wiring bond pad of the inner-metallayer, thus some additional through silicon vias (TSV) may be needed.Accordingly, fabricating a backside illuminated image sensor is morecomplicate and costly than fabricating a front side illuminated imagesensor.

Currently, an improved technology has been adopted by those skilled inthe art, wherein an essential color filter associated with lens isembedded in a front side illuminated image sensor by the conventionallithography process in order to reduce the optical path and improve thequanta efficiency of the front side illuminated image sensor, thus thefront side illuminated image sensor can provide a performancesubstantially similar to that of a backside illuminated image sensor.

However, since the rough and unevenness surface of the embedded colorfilter may adversely affect the subsequent process and yield, thus theembedding deepness of the color filter may be limited. These problemsmay get worse, as the current front side illuminated image sensor isrequired to provide more and more resolution and small pixel size.

Therefore, it is necessary to provide an improved optical microstructurewith a stand-alone color filter associated with micro lens tomanufacture an image sensor with higher quanta efficiency and lowermanufacturing cost, and to improve the long existing cross-talkproblems.

SUMMARY OF THE INVENTION

According to one aspect of the present invention is to provide an imagesensor comprises a plurality of color filtering elements, a plurality oflenses and an image sensing device, wherein the lenses arecorrespondingly formed over the color filtering elements, and the imagesensing device having a sensing area engaged with the color filteringelements.

In some embodiments of the present invention, the color filteringelements are buried in a dielectric layer of the sensing area and with adeepness extending beyond a bottom metal which is disposed in thedielectric layer and adjacent to the sensing area. In some otherembodiments, the color filtering elements are contiguously disposed on abackside of the image sensing device. In some embodiments of the presentinvention, the image sensor further comprises a planarization layerdisposed between the lenses and the color filtering elements.

In some embodiments of the present invention, the image sensor has awafer-scale structure which can be cut into a plurality of image sensingchips.

In some embodiments of the present invention, the image sensor furthercomprises a working substrate and a transparent substrate disposed onthe working substrate, wherein the transparent substrate has a pluralityof recesses allowing the lenses correspondingly embedded therein.

In some embodiments of the present invention, the image sensor furthercomprises a passive layer disposed on the transparent substrate oppositeto the lenses.

According to another aspect of the present invention is to provide amethod for fabricating an image sensor, wherein the method comprisessteps as follows: Firstly, a transparent substrate is formed on aworking substrate. Pluralities of micro lens are formed in thetransparent substrate, wherein the lenses have a refraction ratiodiffering from that of the transparent substrate. Subsequently, a colorfilter is formed on the lenses. Afterward, the color filter is engagedwith an image sensing device by flipping the working substrate.

In some embodiments of the present invention, the engagement of thecolor filter and the image sensing device comprises steps of forming aconcave portion in the sensing area and then contiguously disposing thecolor filter to a bottom of the concave portion. In some otherembodiments, the engagement of the color filter and the image sensingdevice comprises steps of disposing the color filter contiguously to abackside of the image sensing device.

In some embodiments of the present invention, the formation of the colorfilter comprises steps of forming a plurality of color filteringelements over and corresponding to the lenses. In some other embodimentsof the present invention, the formation of the color filter comprisessteps of forming a planarization layer overlying the lenses, and forminga plurality of color filtering elements overlying the planarizationlayer.

In some embodiments of the present invention, after the color filter isengaged with the image sensing device, the working substrate isplanarized, whereby the remaining working substrate can serve as apassive layer to protect the color filter.

In some embodiments of the present invention, after the color filter isengaged with the image sensing device, the working substrate is removedand a passive layer is formed on the transparent substrate opposite tothe lenses.

According to a third aspect of the present invention a method forfabricating an image sensor is to provide, wherein the method comprisessteps as follows: A color filter wafer having a plurality of colorfilters and an image sensor wafer having a plurality of image sensingdevices are firstly provided, wherein each of the image sensing devicehas a sensing area corresponding to one of the color filters.Subsequently, the color filter wafer is engaged with the image sensorwafer to make each of the color filter buried in a dielectric layer ofthe sensing area with a deepness extending beyond a bottom metaldisposed in the dielectric layer and adjacent to the sensing area.

In some embodiments of the present invention, after the color filterwafer and the image sensor wafer are engaged, a wafer sawing process iscarried out to cut the engaged color filter wafer and the image sensorwafer into a plurality of image sensing chips and each at leastcomprises one of the micro lens, one of the image sensing devices andone of the color filters.

According to aforementioned embodiments of the present invention, animproved image sensor and the fabricating method thereof are provided.Instead of directly forming the essential color filter layer on an imagesensing element to form an image sensor by a series complicateprocesses, as the prior art dose; the color filter is formed on anindependent transparent substrate and subsequently engaged to an imagesensing element to form an image sensor. Therefore, the present methodis capable of being applied for fabricating either a BSI image sensor ora FSI image sensor with the advantages of simplifying the packageprocess.

When the independent optical microstructure is applied, especially, forfabricating a FSI image sensor, the color filter can be pre-planrized tosolve the problems and the adverse effects resulted from the roughnessand unevenness surface, thus the color filter can be embedded into theFSI image sensing element more deeply, and the optical path of the FSIimage sensor can be significantly decreased, whereby the quantaefficiency of the FSI image sensor can be significant enhanced, and thelong existing cross-talk problems can also be improved. Since, thefabricating cost of a FSI image sensor is significantly less than thatof a typical BSI image sensor, thus the embodiments of the presentinvention can provide an image sensor with a performance substantiallysimilar to that provided by a typical BSI image sensor but with afabricating cost significantly lower than that of the BSI image sensor.

In order to make the aforementioned and other objects, features andadvantages of the present invention comprehensible, preferred embodimentaccompanied with figures are described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore readily apparent to those ordinarily skilled in the art afterreviewing the following detailed description and accompanying drawings,in which:

FIGS. 1A to 1E illustrate cross views of the processing structures forfabricating an optical microstructure in accordance with one embodimentof the present invention.

FIG. 2 illustrates a cross views of an optical microstructure inaccordance with one embodiment of the present invention.

FIG. 3 illustrates a cross view of a wafer-scale optical microstructure,in accordance with one embodiment of the present invention.

FIGS. 4A to 4D illustrate cross views of the processing structures forfabricating a front side illuminated image sensor in accordance with oneembodiment of the present invention.

FIG. 5 illustrates a cross view of a backside illuminated image sensorin accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Detail descriptions of several embodiments eligible to exemplify thefeatures of making and using the present invention are disclosed asfollows. It must be appreciated that the following embodiments are justexample, but not used to limit the scope of the present invention.Wherever possible, the same reference numbers are used in the drawingsand the description to refer to the same or like parts.

One of the objects of the present invention is to provide an improvedimage sensor having an optical microstructure 100 and the method forfabricating the same. FIGS. 1A to 1E illustrate cross views of theprocessing structures for fabricating an optical microstructure 100 inaccordance with one embodiment of the present invention.

The method for fabricating the optical microstructure 100 comprisessteps as follows: A working substrate 101 (shown in FIG. 1A) isprovided. In some embodiments of the present invention, the workingsubstrate 101 is a glass substrate, a silicon substrate or a siliconwafer.

A transparent substrate 102 contiguous to the working substrate 101 isthen provided (shown in FIG. 1B). In some embodiments of the presentinvention, the transparent substrate 102 can be a preformed transparentboard directly attached onto the working substrate 101. In someembodiments of the present invention, the transparent substrate 102 canbe otherwise a transparent layer structure formed on the workingsubstrate 101 by a deposition process, an electroplating process,printing process, spin coating or the like.

The material consisting of the transparent substrate 102 can be similarto or different from that consisting of the working substrate 101. Insome preferred embodiments, the material consisting of the transparentsubstrate 102 has index refraction different from that of the materialconsisting of the working substrate 101. The preferred materialconsisting of the transparent substrate 102 may be silicon, resin,glass, propylene glycol methyl ether acetate (PGMEA), poly-glycidylmethyl acrylate (PGMA) or the arbitrary combinations thereof.

Next, at least one recess 103 is formed on a top surface 102 a of thetransparent substrate 102 (shown in FIG. 1C). In some embodiments of thepresent invention, the recess 103 is formed by an etching process. Inthe present embodiment, the etching process is conducted on the topsurface 102 a of the transparent substrate 102 to form a patterncomprising a plurality of recesses 103. In some embodiments of thepresent invention, each of the recesses 103 has a cross section shapesas an arc or other geometric patterns, and these recesses 103 may beconnected with one another or departed from each other. In the presentembodiment, each of these recesses 103 has a bottom surface 103 a with across view shapes as a semicircle, and these recesses 103 are connectedwith one another to form an array pattern.

Subsequently, a plurality of lenses 104 are correspondingly formed inthe recesses 103, as shown in FIG. 1D. The lenses 104 preferably consistof a transparent glass, plastic polymers (such as resin, PGMEA, PGMA orthe arbitrary combinations thereof) or a semiconductor material (such assilicon).

In some embodiments of the present invention, the formation of thelenses 104 comprises steps of partially filling the recesses 103 with atransparent material to make the transparent material conformable to thebottom surface 103 a of the corresponding recess 103, and thencoagulating the transparent material. In the present embodiment, thelenses 104 formed in the corresponding recesses 103 are a hemispheretransparent structure consisting of the coagulated transparent material.

In order to serve as a light condenser, the index of the lens 104 shouldbe different from that of the transparent substrate 102. The index ofthe lenses 104 preferably is greater than that of the transparentsubstrate 102.

Afterward, a plurality of color filtering elements 105 a are formed onthe lenses 104 (shown in FIG. 1E). In some embodiments of the presentinvention, each of the color filtering elements 105 a may be a filteringelement with an individual color including red, green, blue, cyan,magenta and yellow, whereby the combination of the color filteringelements 105 a can constitute a color filter 105 with a single color. Insome other embodiments of the present invention, the color filter 105alternately includes a plurality of color filtering elements withvarious colors.

In some preferred embodiments of the present invention, the formation ofthe color filter 105 comprises several steps as follows: Pluralities ofpatterned resists (not shown) are sequentially blanketed over the lens104 associate. A plurality of color filtering elements 105 a withdifferent colors are then formed on the lenses 104 over thecorresponding lenses 104 by using the correspondingly patterned resistas a mask respectively.

In some preferred embodiments of the present invention, each of thecolor filtering elements 105 a may partially fill the correspondingrecess 103, and there remains a gap between the color filter 105 and thetop surface 102 a of the transparent substrate 102. In some otherembodiments of the present invention, each of the color filteringelements 105 a fulfills the corresponding recess 103, whereby the colorfilter 105 may extend over the top surface 102 a of the transparentsubstrate 102.

In order to keep the morphology of the filter 105 flat, a planarizationprocess is conducted to make the cooler filter 105 conformable to thetop surface 102 a of the transparent substrate 102.

As shown in FIG. 1E, the optical microstructure 100 formed by theaforementioned method comprises a working substrate 101, a transparentsubstrate 102, a plurality of the lenses 104 and a color filter 105constituted by a plurality of color filtering elements 105 a. Whereinthe transparent substrate 102 is contiguously disposed on the workingsubstrate 101 and has a plurality of recesses 103 formed on the topsurface 102 a; each of the lenses is disposed in the correspondingrecess 103; and the color filtering elements 105 a are correspondinglydisposed on the lenses 104 and fill the recesses 103, so as to make thecooler filter 105 conformable to the top surface 102 a of thetransparent substrate 102.

FIG. 2 illustrates a cross views of an optical microstructure 200 inaccordance with another embodiment of the present invention. Thephysical structure of optical microstructure 200 is similar to theoptical microstructure 100 (as shown in FIG. 2, identical referencenumbers are used to refer to the identical elements shown in FIG. 1E),the major difference between these two optical microstructures 100 and200 is that the optical microstructure 200 further comprises aplanarization layer 206 disposed between the lenses 104 and the colorfilter 105. In the present embodiment, the planarization layer 206 isformed prior the steps of forming the color filtering elements 105 a onthe lenses 104 to fill the recesses 103.

FIG. 3 illustrates a cross view of a wafer-scale optical microstructure,in accordance with a third embodiment of the present invention. Thephysical structure of optical microstructure 300 is similar to theoptical microstructure 100; however the major difference between thesetwo optical microstructures 100 and 300 is that the opticalmicrostructure 300 (thereinafter is referred as color filter wafer 300)is a wafer-scaled structure having a color filter array 35 constitutedby a plurality of separated lenses 304 and a plurality of separatedcolor filters 305 formed on a working wafer 301. In some embodiments,the color filter wafer 300 may be cut to divide into a plurality ofchips in accordance with the arrangement of the color filters 305,whereby each of the chips has a color filter 305 and can be used toengage with an image sensing element to form an image sensor. In someother embodiments, the color filter wafer 300 is otherwise engaged withan image senor wafer (not shown) which comprises a plurality of imagesensing devices formed on a semiconductor wafer. A wafer sawing processis then is carried out to cut the engaged color filter wafer 300 and theimage sensor wafer into a plurality of image sensing chips (not shown)and each comprises at least one of the micro lens, the image sensingdevice and the color filter. For the suppose of clearly describing thefeatures of the present invention, the engagement of the color filterwafer 300 and the image senor wafer will be illustrated by the followingembodiments which merely comprise one color filter and one image sensingdevice.

FIGS. 4A to 4C illustrate cross views of the processing structures forfabricating a FSI image sensor 40 in accordance with one embodiment ofthe present invention.

The method for fabricating the FSI image sensor 40 comprises steps asfollows: Firstly, an optical microstructure, such as the opticalmicrostructure 100 shown in FIG. 1E, and a FSI image sensing element 400are provided.

As shown in FIG. 4A, the FSI image sensing element 400 comprises asensing area 411 a and a peripheral area 411 b formed on a siliconsubstrate 411 by a front-end-of -line (FEOL) process. In some embodimentof the present invention, the sensing area 411 a comprises at least onephotodiode 410 and at least one transfer gate 408. An inner dielectricmaterial layer 412, and a protection layer 414 are sequentiallyblanketed over the sensing area 411 a and the peripheral area 411 b, andat least one inner-metal layer 413 are buried in the inner dielectricmaterial layer 412 involved in the peripheral area 411 b.

In the present invention, the sensing area 411 a comprising at least onephotodiodes 410 are defined as the region isolated between two shallowtrench isolations (STI) 407 formed in the silicon substrate 411, and theperipheral area 411 b is defined as the region over the two STIs 407 onwhich a portion of the inner-metal layer 413 stacked.

Subsequently, the transparent substrate 102 of the opticalmicrostructure 100 is engaged with the image sensing element 400 to makethe color filter 105 contiguous to the sensing area 411 a.

In some embodiments of the present invention, a concave portion 415 isformed by partially or completely removing the inner dielectric materiallayer 412 and the passive layer 414 involved in the sensing area 411 a(as shown in FIG. 4B) prior the engagement of the optical microstructure100 and the image sensing element 400.

The deepness of the concave portion 415 may vary in accordance with theoptical requirement of the image sensor 40. For example, the concaveportion 415 preferably extends, through the protection layer 414 anddownwards into the inner dielectric material layer 412, at least beyondone of the stacked inner-metal layers, or even extends through theprotection layer 414 and the inner dielectric material layer 412 so asto expose the silicon substrate 411 of the sensing area 411 a.

In the present embodiment, the concave portion 415 is formed by anetching process to remove a portion of the protection layer 414 and aportion of the inner dielectric material layer 412, whereby the concaveportion 415 extends through the protection layer 414 and downwards intothe inner dielectric material layer 412 beyond the top metal layer 413 a(which is also referred as the bottom metal layer). In other words, thebottom 415 a of the concave portion 415 may extend beyond the most topmetal layer 413 a of the stacked inner-metal layers 413 from the innerdielectric material layer 412.

After the formation of the concave portion 415, the opticalmicrostructure 100 is flipped and the filter 105 associated with thetransparent substrate 102 is then embedded into the concave portion 415of the image sensing element 400, whereby the color filter 105 isdisposed contiguous to the bottom 415 a of the concave portion 415, andthe FSI image sensor 40 as shown in FIG. 4C is formed.

It should be noted that the optical microstructure 100 is not onlyapplicable for fabricating a FSI image sensor but also for fabricating aBSI image sensor. FIG. 5 illustrates a cross views of a BSI image sensor50 having the optical microstructure 100 in accordance with oneembodiment of the present invention.

In the present embodiment, a BSI image sensing element 500 is engagedwith the optical microstructure 100 to form the BSI image sensor 50.Similar to the FSI image sensing element 400, the BSI image sensingelement 500 also comprises a silicon substrate 511 having at least onephotodiode 510, a sensing area 511 a, a peripheral area 511 b and aplurality of inner-metal layer 513 buried in a dielectric material 512,wherein the sensing area 511 a and the peripheral area 511 b are formedon the silicon substrate 511 by a FEOL process, and the inner-metallayers 513 and the dielectric material 512 are formed on the sensingarea 511 a and the peripheral area 511 b by a back-end-of-line (BEOL)process. The major difference between the FSI image sensing element 400and the BSI image sensing element 500 is that the BSI image sensingelement 500 further comprises a handle wafer 516 bonded on to thedielectric material 512 and the inner-metal layers 513, and the backside511 c of the silicon substrate 511 is subjected to a thinning processpreceding the engagement of the optical microstructure 100 and the BSIimage sensing element 500.

In the present embodiment, the engagement of the optical microstructure100 and the BSI image sensing element 500 comprises steps as follows:The color filter 105 of the optical microstructure 100 is aligned withthe sensing area 511 a of the BSI image sensing element 500, and thecolor filter 105 is then attached on to the backside 511 c of thesilicon substrate 511 before the working substrate 101 is removed. Aftersubsequent wiring and packaging processes, a plurality of throughsilicon vias (TSV) 509 and bond pads 510 electrically connected to theinner-metal layers 513 are formed, and the BSI image sensor 50 iscompleted.

In addition, the working substrate 101 can be either removed or remainedafter the optical microstructure 100 is engaged with the FSI imagesensing element 400 (or BSI image sensing element 500). For example, insome embodiments, the working substrate 101 is thoroughly or partiallyremoved and the remaining portion may serve as a passive layer toprotect the color filter 105 and the lenses 104. In some embodiments ofthe present invention, a releasing film (not shown) may be disposedbetween the working substrate 101 and the transparent substrate 102,whereby after the optical microstructure 100 is engaged with the FSIimage sensing element 400 (or the BSI image sensing element 500), theworking substrate 101 can be released from the transparent substrate 102and reused again.

In some other embodiments of the present invention, a grinding processis conducted to remove the working substrate 101 or even a portion ofthe transparent substrate 102. Although the exposed transparentsubstrate 102 can serve as a passive layer to protect the color filter105 and the lens 104, in some preferred embodiments, an additionalplanarization or package process may conducted on the transparentsubstrate 102 to form a polarization layer or a passive layer 418(518),shown in FIG. 4D (FIG. 5) 102, to serve as a protection layer or apassive layer of the color filter layer and the lenses 104. In thepresent embodiment, a passive layer 418(518) consisting of silicon,glass or the like, is attached on the transparent substrate 102 by apackage process.

According to aforementioned embodiments of the present invention, animproved image sensor and the fabricating method thereof are provided.Instead of directly forming the essential color filter layer on an imagesensing element to form an image sensor by a series complicateprocesses, as the prior art dose; the color filter is formed on anindependent transparent substrate and subsequently engaged to an imagesensing element to form an image sensor. Therefore, the present methodis capable of being applied for fabricating either a BSI image sensor ora FSI image sensor with the advantage of simplifying the packageprocess.

When the independent optical microstructure is applied, especially, forfabricating a FSI image sensor, the color filter can be pre-planrized tosolve the problems and the adverse effects resulted from the roughnessand unevenness surface, thus the color filter can be embedded into theFSI image sensing element more deeply, and the optical path of the FSIimage sensor can be significantly decreased, whereby the quantaefficiency of the FSI image sensor can be significant enhanced, and thelong existing cross-talk problems can also be improved. Since, thefabricating cost of a FSI image sensor is significantly less than thatof a typical BSI image sensor, thus the present invention can provide animage sensor with a performance substantially similar to that providedby a typical BSI image sensor but with a fabricating cost significantlylower than that of a BSI image sensor.

The present invention has been disclosed above in the preferredembodiments, but is not limited to those. It is known to persons skilledin the art that some modifications and innovations may be made withoutdeparting from the spirit and scope of the present invention. Therefore,the scope of the present invention should be defined by the followingclaims.

1. An image sensor, comprising: a plurality of color filtering elements;a plurality of lenses correspondingly formed over the color filteringelements; and an image sensing device having a sensing area engaged withthe color filtering elements.
 2. The image sensor of claim 1, whereinthe color filtering elements are buried in a dielectric layer of thesensing area and with a deepness extending beyond a bottom metal whichis disposed in the dielectric layer and adjacent to the sensing area. 3.The image sensor of claim 1, further comprising a planarization layerdisposed between the plurality of lenses and the plurality of colorfiltering elements.
 4. The image sensor of claim 1, wherein the colorfiltering elements are contiguously disposed on a backside of the imagesensing device.
 5. The image sensor of claim 1, wherein the image sensorhas a wafer-scale structure which can be cut into a plurality of imagesensing chips.
 6. The image sensor of claim 1, further comprising: aworking substrate; and a transparent substrate disposed on the workingsubstrate, wherein the transparent substrate has a plurality of recessesallowing the lenses correspondingly embedded in the recesses.
 7. Theimage sensor of claim 1, wherein the image sensor further comprises apassive layer disposed on the transparent substrate opposite to thelenses.
 8. A method for fabricating an image sensor, comprising: forminga transparent substrate on a working substrate; forming pluralities ofmicro lens in the transparent substrate, wherein the lenses have arefraction ratio differing from that of the transparent substrate;forming a color filter on the lenses; and engaging the color filter withan image sensing device by flipping the working substrate.
 9. The methodfor fabricating the image sensor of claim 8, wherein the engagement ofthe color filter and the image sensing device comprises steps of:forming a concave portion in the sensing area; and contiguouslydisposing the color filter to a bottom of the concave portion.
 10. Themethod for fabricating the image sensor of claim 8, wherein theengagement of the color filter and the image sensing device comprisessteps of disposing the color filter contiguously to a backside of theimage sensing device.
 11. The method for fabricating the image sensor ofclaim 8, wherein the formation of the color filter comprises steps offorming a plurality of color filtering elements over and correspondingto the lenses.
 12. The method for fabricating the image sensor of claim8, wherein the formation of the color filter comprises steps of forminga planarization layer overlying the lenses, and forming a plurality ofcolor filtering elements overlying the planarization layer.
 13. Themethod for fabricating the image sensor of claim 8, further comprisingplanarizing the working substrate, whereby the remaining workingsubstrate can serve as a passive layer to protect the color filter,after the color filter is engaged with the image sensing device.
 14. Themethod for fabricating the image sensor of claim 8, wherein after thecolor filter is engaged with the image sensing device, furthercomprising removing the working substrate; and forming a passive layeron the transparent substrate opposite to the lenses.
 15. A method forfabricating an image sensor, comprising: providing a color filter waferhaving a plurality of color filters; providing an image sensor waferhaving a plurality of image sensing devices, wherein each of the imagesensing device has a sensing area corresponding to one of the colorfilters; and engaging the color filter wafer with the image sensor waferto make each of the color filter buried in a dielectric layer of thesensing area with a deepness extending beyond a bottom metal disposed inthe dielectric layer and adjacent to the sensing area.
 16. The methodfor fabricating the image sensor of claim 15, wherein after the colorfilter wafer and the image sensor wafer are engaged, a wafer sawingprocess is carried out to cut the engaged color filter wafer and theimage sensor wafer into a plurality of image sensing chips each at leastcomprises one of the micro lens, one of the image sensing devices andone of the color filters.